C Pointers and Arrays

by CodeCapsule

1. Array Name as a Pointer

In C, the name of an array is treated as a pointer to its first element.
That means:

numbers → address of the first element (numbers[0])

2. Accessing Array Elements Using Pointers

Using pointer arithmetic

Output:

*(ptr + i) accesses the i-th element by moving the pointer.

Equivalent Using Array Index

numbers[i] is the same as *(numbers + i) in C.

3. Modifying Array Elements Using Pointers

#include <stdio.h>

int main() {
int numbers[5] = {1, 2, 3, 4, 5};
int *ptr = numbers;

for (int i = 0; i < 5; i++) {
*(ptr + i) = *(ptr + i) * 2; // double each element
}

for (int i = 0; i < 5; i++) {
printf("%d ", numbers[i]);
}

return 0;
}

#include <stdio.h>

int main() {

int numbers[5] = {1, 2, 3, 4, 5};

int *ptr = numbers;

for (int i = 0; i < 5; i++) {

*(ptr + i) = *(ptr + i) * 2; // double each element

}

for (int i = 0; i < 5; i++) {

printf("%d ", numbers[i]);

}

return 0;

}

Output:

4. Array of Pointers

You can also have an array of pointers, each pointing to a variable or string.

Output:

Useful for storing multiple strings efficiently.

5. 2D Arrays and Pointers

A 2D array can be accessed using pointers:

#include <stdio.h>

int main() {
int matrix[2][3] = {{1, 2, 3}, {4, 5, 6}};
int (*ptr)[3] = matrix; // pointer to array of 3 ints

for (int i = 0; i < 2; i++) {
for (int j = 0; j < 3; j++) {
printf("%d ", ptr[i][j]);
}
printf("\n");
}

return 0;
}

#include <stdio.h>

int main() {

int matrix[2][3] = {{1, 2, 3}, {4, 5, 6}};

int (*ptr)[3] = matrix; // pointer to array of 3 ints

for (int i = 0; i < 2; i++) {

for (int j = 0; j < 3; j++) {

printf("%d ", ptr[i][j]);

}

printf("\n");

}

return 0;

}

Output:

6. Key Points About Pointers and Arrays

Array name = pointer to first element.
Access elements with pointer arithmetic: *(ptr + i) = array[i].
Pointers can modify array elements directly.
Array of pointers can store multiple strings efficiently.
For 2D arrays, pointer-to-array syntax: int (*ptr)[cols].

C Pointers and Arrays

1. Array Name as a Pointer

2. Accessing Array Elements Using Pointers

Using pointer arithmetic

Equivalent Using Array Index

3. Modifying Array Elements Using Pointers

4. Array of Pointers

5. 2D Arrays and Pointers

6. Key Points About Pointers and Arrays

You may also like...

Leave a Reply Cancel reply

C Pointers and Arrays

1. Array Name as a Pointer

2. Accessing Array Elements Using Pointers

Using pointer arithmetic

Equivalent Using Array Index

3. Modifying Array Elements Using Pointers

4. Array of Pointers

5. 2D Arrays and Pointers

6. Key Points About Pointers and Arrays

You may also like...

C Errors

C string.h Library

C String Functions

Leave a Reply Cancel reply